#1 Re: Hardware » How important is the ADC BIAS resistor precision for decoding? » 2015-12-01 11:19:29

Hi Taner,

I have made one experiment. When i use lm1117 and an 5% resistors i got like 10% less decoded packet then when i use precision voltage regulator like TC1014 and 1% resistors. So i think it make a big difference.


#2 Re: General discussion » Micro APRS Tracker. » 2015-10-04 17:09:05

5B4ALR wrote:

On lines 268, 269, says the same thing. And IDE says: " 'APRS_sendStat' was not declared in this scope" .

Ok that was my mistake. I have changed the LibAPRS a little bit so it can send also status massages, and i forgot about it.
I have removed that from the sketch.
About receiving packets. I have no problem at all now. Here where i live i receive about 1-2 packets per second.

#3 Re: General discussion » Micro APRS Tracker. » 2015-09-18 21:14:05

I have updated the sketch in GitHub. The tracker works fine now. It decodes packages whiteout any problem. But i have removed the readVCC function for now.
Here is one small post i have write about this project: http://www.lz1ppl.com/2015/09/micro-aprs-tracker/

#4 Re: General discussion » Micro APRS Tracker. » 2015-09-15 18:42:54

Hi all,
Thank you for the suggestion.
Stanly actually you was on the right track, but the problem was in the readVCC function. When i disable it i start to receive packets. Now i have some small problem whit the overflow of the ram memory but i hope i will solve this fast. I hope that i will have time this weekend and will work on that. When i have working solution i will update the sketch in Github.

Thanks again for you suggestions.

73 de LZ1PPL

#5 General discussion » Micro APRS Tracker. » 2015-09-07 09:55:07

Replies: 6

Hi all,

The post of Taner DB1NTO has inspired me to do my one APRS tracker.
I have made the tracker using Mark's LibAPRS.

Here is what i have done till now.
FluxBB bbcode test FluxBB bbcode test

Im using the code i have posted on Github https://github.com/LZ1PPL/VSTv2/blob/master/VSTv2.ino

I have made some tests. The tracker sends position whiteout any problem. The smart-beacon works like a charm.

The only problem that i have is that i cant decode any APRS massages that I'm receiving.
When i use this code: https://github.com/LZ1PPL/VSTv2/blob/master/Recive.ino
I'm seeing the received massages on the Oled display. So the problem is not on the hardware side. The problem is probably something on my code that i can not see. If anyone find a solution i will be really thankful.

The sketch in GitHub is updated.
Now the tracker sends and decodes packages.
The readVCC function is removed for now.

73 de LZ1PPL

#6 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-27 09:06:50

la3bna wrote:

Can someone pleas measure the ohms that they find work with DRA818 radio. I mean on the Potmeter. (I dont hav a 100K pot so Im not sure I got the correct value on my resistor)

I have connected the pot as i have shown here https://drive.google.com/file/d/0Bz49Vw … sp=sharing . I'm using 10k pot and its set just in the middle. I have measured the ohms and they are 5k to ground and 5.1k to resistor ladder. This works just fine for me.

la3bna wrote:

If you are going to use the DRA818 the you could do this to AFSK.cpp

Line 461 -471

ISR(ADC_vect) {
    TIFR1 = _BV(ICF1);
    AFSK_adc_isr(AFSK_modem, ((int16_t)((ADC) >> 2) - 0x80));
    if (hw_afsk_dac_isr) {
        DAC_PORT = (AFSK_dac_isr(AFSK_modem) & 0xF0) & ~_BV(3); 
		} else {
      DAC_PORT = 0x88;

I will try this.

la3bna wrote:

If you use Eagel I have been fiddeling a bit with a tracker PCB that has DRA818 and separate GPS (PA6H ) PCB.

I'm using Eagle and i have designed one PCB for the tracker already, but I'm trying to add second serial port so i can program the setup parameters from the serial whiteout using the arduino IDE. The main problem is that the free ram is to little whit the sketch i have posted. so I'm trying to optimize it. I have even write my one GPS sentence parsing so i can remove the TinyGPS++ library. But i have some problems, everything works fine until i include and start the APRSLib. When the library is induced the tracker start to lose some packets and the whole thing just doesn't work as it should be.
I will try some different methods for parsing and if nothing work i just will leave that idea for the second serial port.

#7 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-17 09:12:53

You can't change A4 and A5 pins they are the hardware i2c. I haven't seen  arduino whiteout this pins. Can you please post pictures of top and bottom side of you arduino.
You can check this picture for reference. http://webdca.com/abd/images/pinout-ard … o-mini.png

#8 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-14 09:32:48

Im using the standard LibAPRS, TinyGPS++ and U8glib Libraries and Arduino1.0.5. I just downloaded the code from Github and the library's in a clean install of Arduino and it compiled whiteout any problem. I tried also Arduino 1.6.0 and 1.6.1 also no problems at all. I even tied on another freshly installed pc also no problems. So i have no idea know what you are doing wrong.

Plamen LZ1PPL

#9 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-10 08:19:12

Stanley wrote:

On the circuit, something to add, according to the manufacturer, the radio shd be connected to Li-On ( 3.7-4.2V) instead of 3.3V regulator as the 3.3V source would not be able to draw the required current during 1W tx ..

Thats correct.
And one more thing i have missed on the circuit barbecue i was in a hurry. The analog reference pin on the atmega should be connected to regulated 3.3v.

#10 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-09 22:05:41

Here is the schematic im using. https://drive.google.com/file/d/0Bz49Vw … sp=sharing

You can check the signals from you arduino. Pin 3 should be low when not transmitting and high when transmitting. This is the PTT pin. After the transistor you should have high when not transmitting and low when transmitting, the DORJI module ptt is active when its connected to ground.
Digital pins 4, 5 and 6 should be low when not sending data and digital pin 7 should be high. Wen sending data pins 4, 5 and 6 should go to high and pin 7 to low. Whit the trimer you can set up the voltage level that is going to the mic in of the dorji module.

P.S.: My English is not perfect but i hope you will understand what i wanted to say.


#11 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-09 14:08:29

Ok. With the serial monitor the AT+DMOSETGROUP commands is the only thing you will see. I haven't added any kind of diagnostic massages because im very low on ram, but the rest is very strange. The module should transmit once every 15 min. for a period of 2 3 sec. I will try to post some schematics of my project later tonight so you can check the connections.
But at the moment im at work and cant give you any suggestions. I will try to do it later tonight.

#12 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-03-01 06:42:30

WA6MAT wrote:

Do you have a basic schematic? I dont need much, just which pins go where(since i seem to have missed it 100% in your code)

The OLED display is connected to A4 A5(I2C). The GPS module is connected to RX pin. The DORJI module to TX. The rest is like the MicroModem schematic.


#13 Re: General discussion » PicoAPRS, world's smallest APRS Transceiver with KISS TNC » 2015-02-28 23:31:51

Hi Taner,

Whit your code as a base and LibAPRS I have made battery powered APRS Tracker whit one Arduino Pro Mini. I have added additional information on the display for the battery voltage and Maidenhead locator.
I haven't tested the receive function yet but it transmits correct.
I know that my code is not perfect and i plan to optimize it, but for now its working fine.

You can see the code here: https://github.com/LZ1PPL/VSTv2/blob/master/VSTv2.ino

I still intend to do some thing about this project when i have a free time.
1. Optimize the code.
2. Add option to setup some variables true PC.
3. Make a PCB for the tracker.

73's to all

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